Several methods for fabricating semiconductor devices utilize a plasma generated or maintained within a processing chamber. The character of the plasma within the chamber has an important effect upon the results of the fabrication process, such as etching or chemical vapor deposition.
For example, the quality of the plasma generated may be characterized by high density ion generation and ion energy control. One kind of plasma reactor of interest is the inductively coupled plasma reactor. The plasma in such a reactor is generated inside a vacuum chamber by a coiled RF antenna, typically located on the ceiling dome and/or sides of the plasma chamber.
By adjusting the RF current in the antenna, the density of the ions can be controlled. The energy of the ions can be controlled by another RF power, usually called RF bias, that is connected to the wafer pedestal. However, ion energy is not mono-energetic, and ion energy distribution is dependent on many factors, including but not limited to bias power and frequency, ion species, and plasma density.
One factor affecting the quality of the process on the wafer is fluctuation in dome temperature. Fluctuation in dome temperature may generate particles that deposit on the wafer and may result in nonuniformity and lack of repeatability of a deposited film of material. In addition, variation in temperature over regions of the dome may result in excessive mechanical stress that can ultimately result in dome fracture.
Another issue faced by the designers of plasma generation chambers is capacitive coupling between the RF antenna and the ions of the plasma. Increased capacitive coupling between the antenna and the plasma can give rise to an elevated plasma potential in the proximity of the dome surface, thereby increasing the energy of the ions impinging on the dome surface. High ion energies give rise to excessive ion bombardment on the dome wall adjacent to the RF antenna, thereby increasing the number of contaminant particles and the rate of wear of the chamber.
A number of techniques can be employed alone or in conjunction to reduce capacitive coupling. In one approach, a Faraday shield can be placed between the RF antenna and the generated plasma. The Faraday shield is a grounded conductive layer that includes narrow, elongated openings having a major axis perpendicular to the windings of the RF coil antenna. These openings act to suppress any eddy currents that would otherwise tend to be induced in the Faraday shield. The conductive, fixed potential plane of the Faraday shield prevents capacitive coupling from voltage oscillations in the coil to the plasma. The suppression of eddy currents allows the inductive coupling of the electromagnetic field to couple to the plasma.
Given the importance of plasma-based processes to the fabrication of semiconductor devices, methods and structures permitting enhanced durability and reliability of plasma-based fabrication apparatuses are desirable.
The temperature of a plasma chamber of a semiconductor fabrication tool and hence the character of the plasma generated therein, may be maintained substantially constant utilizing a variety of techniques alone or in combination. One technique is to provide an exterior surface of a dome overlying the plasma chamber with a plurality of projecting fins effective to conduct heat from the chamber into an overlying circulating airflow defined between the dome and a dome cover. The dome cover may further define projecting lips or an airfoil structure that place the circulating airflow into intimate contact within the dome surface. Other techniques include employing an independently-controlled high speed fan to drive the airflow circulation, and the use of sensors in the dome to precisely monitor temperature.
An embodiment of a substrate processing chamber in accordance with the present invention comprises a housing having a processing region and a substrate support to support a substrate for processing in the processing region. The housing includes a chamber top which has an external surface, wherein a plurality of heat conducting fins project from the external surface of the chamber top.
An embodiment of a substrate processing apparatus in accordance with the present invention comprises a processing chamber including a side and a top, and a top RF source configured to apply top RF energy to the processing chamber through the top. A side RF source is configured to apply side RF energy to the processing chamber through the side, and a plurality of heating members are configured to apply thermal energy to different regions of the processing chamber, the plurality of heating members having thermal outputs which are regulated to provide a generally uniform temperature in the processing chamber.
An alternative embodiment of a substrate processing apparatus in accordance with the present invention comprises a processing chamber including a side and a top, and a cover spaced above the top to define a fluid pathway between an inner surface of the cover and an external surface of the top, the fluid pathway extending radially from an inlet located near a center of the top to and outlet located around a periphery of the top to permit a fluid flow therethrough. At least one flow diverter is disposed in the fluid pathway to divert the fluid flow against the external surface of the top.
An embodiment of a dome structure in accordance with the present invention for a semiconductor processing tool comprises a ceramic member configured to form a portion of a housing defining a chamber of the semiconductor processing tool. A fin is configured to project from an external surface of the ceramic member.
An embodiment of a method for maintaining substantially constant a temperature of a plasma processing chamber subjected to an applied RF power to generate a plasma therein, comprises providing a fin on an exterior surface of the chamber. A flow of a cooling fluid is caused to contact the fin and convey thermal energy away from the chamber.
These and other embodiments of the present invention, as well as its features and some potential advantages are described in more detail in conjunction with the text below and attached figures.